1. Field of the Invention
This invention relates generally to a reel for tape, and more particularly, is directed to a reel on which a magnetic tape is wound for use in a magnetic recording and/or reproducing apparatus.
2. Description of the Prior Art
A tape cassette for a cassette type V.T.R. (Video Tape Recorder) contains a pair of reels. FIG. 1 shows an existing reel which comprises a pair of segmental reel hubs 2 and 3 and a pair of upper and lower flanges 4 and 5. The segment 2, having an angular extent if 180.degree. and, the segment 3 also having an angular extent of 180.degree. form one circular reel hub. The segment 2 and the lower flange 5 are moulded integrally of synthetic resin. Further, a boss 6 is formed integrally with the lower flange 5. A circular recess 7 is defined in the top of the boss 6. Six pins 8 are projected from the recess 7. On the other hand, a projected portion 9 is formed at the center of the upper flange 4. The projected portion 9 is projected downward and is fitted in the recess 7. When the projected portion 9 is received in the recess 7, the six pins 8 extend through respective small holes 10 which are formed in the projected portion 9. And then the top ends of the pins 8 are deformed thermally, whereby the upper flange 4 is connected with the boss 6 formed on the lower flange 5.
As shown in FIG. 2, the boss 6 is hollow to provide a socket 15 to receive a reel drive shaft (not shown). Oblong projections 16 are formed axially on the surface of socket 15 and the projections 16 engage with grooves formed on the peripheral surface of the reel drive shaft. Thereby, the reel 1 is driven by the reel drive shaft which is provided on the V.T.R. apparatus.
The segment 3, which is separated from the flanges 4 and 5, provides a pair of detents 11, and corresponding to these detents 11, a pair of engaging portions 12 are formed on the segment 2. Therefore, the detents 11 engage with the engaging portions 12 to connect the segment 2 and segment 3 to each other. Further, one end of a magnetic tape, which is wound on the reel 1, is pinched between one of the detent 11 and the respective engaging portion 12 and is affixed to the reel 1. A pair of oblong openings 13 are formed on the upper flange 4 so that a screw-driver or other tool may be inserted therethrough to disengage the detents 11 from the engaging portions 12.
When a magnetic tape 20 is wound on the peripheral surface of the reel 1, as shown in FIG. 3, tape 20 exercises inward forces in the radial direction against the segments 2 and 3 owing to the tension of the magnetic tape 20. The segment 2 receives the force not only with ribs 14, but also with the lower flange 5 which is formed integrally with the segment 2. Accordingly, the outer surface of segment 2 is not deformed even at the intermediate portion between the ribs 14.
However the segment 3 receives the inner force only with the ribs 14, because the segment 3 is separately moulded from the flanges 4 and 5. Accordingly, the outer surface of segment 3 deforms at the intermediate portions between the ribs 14, and the segment 3 becomes polygonal as shown in FIG. 3. Accordingly, the magnetic tape 20 is stretched intermittently in the direction of the tape length. Thus, the irregularly, tensioned tape causes tracking errors when the video signals are reproduced from the tape by the V.T.R. apparatus. The shrinking of the tape 20 owing to the decrease of the temperature also causes the deformation of the segment 3 as shown in FIG. 3, and adversely affects the magnetic tape 20.